1. Field of the Invention
The present invention relates to a fundus imaging apparatus that images a fundus of an eye to be examined and a method therefor.
2. Description of the Related Art
Conventional fundus cameras form on an image sensor an image reflected from a fundus of an eye to be examined and display on a display unit a fundus image, which is output from the image sensor, to be used for accurate positioning and focusing with respect to the eye to be examined.
The fundus image displayed on the display unit is electronically or optically provided with a mask that has an opening portion at a center thereof to specify a predetermined angle of field of the fundus image. A magnification is determined by a length of a shorter side (vertical direction) of a display unit or a display area having different vertical and horizontal lengths in a shorter side (vertical) direction and a length of the opening portion of the mask in the vertical direction of the display unit. The length of the shorter side (vertical direction) of the display unit is defined longer than that of the opening portion of the mask in the shorter side (vertical) direction of the display unit.
Further, to enlarge and observe a optic disk and a macular area of the fundus image, fundus cameras are known in which the fundus image is optically or electrically enlarged. Japanese Patent Application Laid-Open No. 5-192299 discusses a fundus camera capable of electronically enlarging and displaying an area specified at a specified display magnification by an operator when the operator observes the fundus image before shooting.
On the other hand, along with growing popularity of general-purpose digital cameras in recent years, the general-purpose digital camera is often used for the fundus camera. Further, in recent years, a method is discussed in which a general-purpose digital camera is mounted onto an optical system of the fundus camera, the image sensor provided in the general-purpose digital camera captures the fundus image, and then the captured fundus image is displayed on the display unit of the general-purpose digital camera.
The fundus camera, which is discussed in Japanese Patent Application Laid-Open No. 5-192299, enlarges the image immediately before shooting during the observation, and thus does not enlarge the image from when the observation is started until immediately before the image is captured. Therefore, when the fundus image that is not enlarged is displayed on a small display unit, the fundus image is displayed small, and therefore it is difficult for an operator to perform accurate positioning and focusing.
However, many general-purpose digital cameras include a small display unit. Since the fundus image is used for accurate positioning or focusing with respect to the eye to be examined, it is difficult to clearly observe the fundus image displayed on such a small display unit of the general-purpose digital camera.